[FIX] account: payment terms looking properly with dark mode

Steps to reproduce:

- Install account.
- Go to Payment terms, and select any term (or create a new one).
- In the form, we can see a description box with some darker color.
- Now activate Dark Mode.

We don't need to apply a different background to these payment terms.
Based on similar field in the rest of odoo is better to remain without
any background.

opw-3465888

closes odoo/odoo#138852

X-original-commit: 9c13d961763df9e6a1359cc4645842c055c6d931
Signed-off-by: Andrea Grazioso (agr) <agr@odoo.com>
Signed-off-by: Maruan Aguerdouh Mohtar (magm) <magm@odoo.com>

addons/account/views/account_payment_term_views.xml

@@ -79,7 +79,7 @@
                                     on
                                     <field name="example_date" class="fw-bold oe_inline"/>
                                 </div>
-                                <div colspan="2" style="background:#e0e0e0" class="pt4 pb4">
+                                <div colspan="2">
                                     <field name="note" placeholder="e.g. Payment terms: 30 days after invoice date"/>
                                     <field name="example_preview_discount" class="ps-2"
                                            invisible="not early_discount or not display_on_invoice"/>